考虑季节性温湿变化的混凝土桥梁徐变计算模型研究

为研究温湿变化对混凝土桥徐变效应的长期影响,建立考虑季节性温湿变化的混凝土桥徐变计算模型。该模型以卢志芳模型为基础,选取我国6个典型温湿度特征城市,基于徐变系数非减原则,建立温湿度时变函数,利用多项式累加和积改进卢志芳模型,得到改进徐变模型。将该模型应用于某预应力混凝土连续梁桥(假设该桥分别位于6个城市)10年徐变效应分析中,计算温湿变化、单温变及单湿变下的徐变效应,与规范结果对比表明:在大温湿变化地区,改进徐变模型计算的徐变系数较规范结果增大1.8%(成都)~10.1%(太原),跨中挠度较规范结果最大增加11.8%(太原),温湿变化对徐变效应影响较大;改进徐变模型计算的徐变系数随时间逐渐增长,克服了卢志芳模型在温湿变化较大时可能出现徐变系数下降的缺陷。

Study of Creep Calculation Model for Concrete Bridges Considering Seasonal Temperature and Humidity Variation

To study the long-term influence of temperature and humidity variation on creep effect in concrete bridge,a creep calculation model of concrete bridge taking into account the seasonal temperature and humidity variation was built up.The model takes Lu Zhifang′s model as the basis and the temperature and humidity statistics of six representative cities in China were referenced.Based on the non-decreasing principle of creep coefficient,the time-varying function of temperature and humidity was established,by which the polynomial cumulative sums were gained and employed to upgrade the Lu Zhifang's model to obtain the improved creep model.The model was applied to analyze the 10-year creep effect in prestressed concrete continuous girder bridges,supposing that these bridges are in six different cities,and calculate the temperature and humidity variation and the creep effect under the action of pure temperature variation and pure humidity variation,respectively,and the calculated results were compared with those prescribed in the code.The comparison show that for the area with great seasonal temperature and humidity variation,the creep coefficient calculated by the improved creep model is 1.8%(Chengdu)and-10.1%(Taiyuan)bigger than the conventional data and the midspan deflection displays the maximum increase,11.8%(Taiyuan),proving that the temperature and humidity variation can exert great influence on the creep effect.The creep coefficient calculated by the improved creep model shows sign of time-dependent increase,which is considered a development of the Lu Zhifang's model,because the latter can generate decreased creep coefficient when the temperature and humidity variation is big.